Plant pathogen Macrophomina phaseolina may be emerging cause of ocular infection in humans
A case report highlights the pathogen’s potential to cause severe, devastating ocular infections, despite aggressive treatment
In the literature review, M. phaseolina infections had unfavourable outcomes in 46.15% of cases despite antifungal treatment. Image credit: ©angellodeco – stock.adobe.com
A recent Greek study identified that Macrophomina phaseolina, a fungal phytopathogen that predominantly affects plants, also might be consequential in human health, according to co-authors Panagiotis Toumasis, MD, and Georgia Vrioni, MD, both affiliated with the Department of Microbiology, Medical School, National and Kapodistrian University of Athens, Athens.
“M. phaseolina, a common plant pathogen, is an uncommon but emerging cause of human infections,” they commented. While it affects more than 500 plant species worldwide, it rarely causes disease in humans.
They reported a case of endophthalmitis and undertook a literature review to identify previous infections with this pathogen.
Case of M. phaseolina
The patient in the case study was a 78-year-old man who presented with photophobia and intense pain in the right eye of 10 days duration, which responded to oral analgesics. He reported having a superficial corneal injury that occurred 3 months previously caused by a “metal burr” while working in a field. He received a topical treatment. Two months later, he underwent conjunctival flap surgery for a corneal ulcer that did not heal. He was wearing therapeutic contact lenses and using cyclopentolate 1%, dexamethasone 0.1%, ofloxacin 0.3% and tobramycin 0.3% drops, and applying an eye ointment containing dexpanthenol.
The best-corrected visual acuities were 18/20 and light perception in the left and right eyes, respectively. The right eye was noteworthy for oedema and redness of the upper and lower eyelids, conjunctival congestion and hyperoemia and corneal melting, with about 1 mm of hypopyon. B-scan ultrasonography showed low-amplitude mobile echoes, vitreous membranes and thickening of the retina and choroid. Endophthalmitis was suspected, the authors reported.
Corneal scrapings and vitreous humour samples were obtained for analysis at presentation. Ultimately, a fungal hyphae was identified. Immediate treatment was begun with voriconazole 0.02% and amikacin eye drops, intravenous voriconazole and moxifloxacin was started. An intravitreal injection of voriconazole and amikacin was administered at the same time because the clinical and microscopy findings were suggestive of fungal keratitis-induced endophthalmitis, later confirmed by reverse transcriptase polymerase chain reaction.
No improvement was seen in the patient’s clinical condition. Computed tomography suggested a localised infection of the ocular structures. The intravenous treatment was changed to amphotericin B and isavuconazole, topical voriconazole and amikacin were continued and vancomycin eye drops were added.The patient’s condition worsened and he did not respond to antifungal treatment. The eye was ultimately enucleated to prevent spread, alleviate pain, and reduce the risk of systemic involvement. While there was no evidence of fungal elements in the surrounding orbital tissues, systemic antifungal therapy with intravenous amphotericin B and isavuconazole was continued to ensure the eradication of any potential residual fungal infection. The patient improved and he continued on oral isavuconazole 100 mg twice daily for 4 weeks.
Literature search
The literature review identified 12 patients, for a total of 13 including the current case, in Canada, India, the US and Greece. A range of presentations in humans was seen that included ocular infections in 76.9% of patients (nine cases of keratitis, one of endophthalmitis), skin infections in 15.4% of cases and combined skin/joint infection in 7.7%.
The M. phaseolina ocular infections were linked to ocular trauma/injury by a foreign body in 70%, the authors reported.
Regarding the clinical outcomes of M. phaseolina infections, 46.15% (six cases) had unfavourable outcomes, despite antifungal treatment, requiring surgery. All cases with unfavourable outcomes were associated with ocular infections, they reported.
In commenting on their findings, the investigators said, “This case report of endophthalmitis highlights the pathogen’s potential to cause severe ocular infections with devastating outcomes, even despite aggressive treatment. The systematic review of previously reported human infections emphasises the diverse clinical presentations, ranging from superficial skin infections to more invasive conditions like the one we described. However, M. phaseolina appears to be a fungal phytopathogen with a predilection for ocular infections in humans. Timely diagnosis remains a challenge due to its rarity in clinical settings and the absence of standardised treatment guidelines. However, early identification and appropriate antifungal therapy are critical for favourable outcomes.”
They advised that clinicians become aware of M. phaseolina as a potential emerging pathogen in vulnerable patients and that additional research elucidates the pathogenesis of fungal infections caused by plant pathogens in humans, identifies evidence-based therapeutic strategies, and develops effective preventive measures to minimise impact on clinical outcomes and public health.
